A371786 a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(4*n-k,n-2*k).

1, 4, 27, 209, 1716, 14553, 125971, 1105885, 9809019, 87691592, 788832045, 7131655908, 64743390321, 589808771881, 5389066722654, 49365637128655, 453212161425716, 4168951499299185, 38415242186255419, 354527945536409116, 3276414018301664025

Offset

0,2

Links

Table of n, a(n) for n=0..20.

Formula

a(n) = [x^n] 1/((1-x+x^2) * (1-x)^(3*n)).

Prog

(PARI) a(n) = sum(k=0, n\2, (-1)^k*binomial(4*n-k, n-2*k));

Crossrefs

Cf. A024718, A371785, A371787.

Cf. A371743.

Sequence in context: A091121 A026005 A059391 * A190738 A361717 A275607

Adjacent sequences: A371783 A371784 A371785 * A371787 A371788 A371789

Keyword

nonn

Author

Seiichi Manyama, Apr 06 2024

Status

approved